The present invention relates to hydraulic compositions and high-strength composite materials using blast furnace slag powder. Particularly, the present invention relates to the hydraulic compositions and high-strength composite materials which can be used as interior or exterior building materials, structural materials and such.
Blast furnace slag powder is by-produced in bulk in the process of production of pig iron, and the gross amount of such slag powder produced reaches the order of tens of millions of tons annually. Many studies and attempts have been and are being made for effective utilization of blast furnace slag powder. A method of utilization of blast furnace slag powder is known in which by making use of potential hydraulic properties of blast furnace slag powder, it is added in an amount of several to several ten % to cement (ordinary Portland cement) to form so-called slag cement. In this method, however, blast furnace slag is used as an "annex" and merely constitutes a minor component of the cement.
Few reports are available on the successful preparation of a useful material which is mainly composed of blast furnace slag powder itself. The reason for backwardness in utilization of blast furnace slag powder is that although it is known that blast furnace slag powder is caused to exhibit its potential hydraulic properties by the addition of water and an alkali agent or a sulfate and its hardening (hydration) proceeds gradually, the produced hardened material is so frangible that it can hardly stand practical use.
Attention has been focused on the fact that the hardened body of blast furnace slag powder is weak in strength, especially in bending strength, and many studies have been made for the improvement of this point in recent years. However, the bending strength that could be achieved so far in the efforts for improvement of said hardened body of blast furnace slag powder remains in the range of 50-240 kgf/cm.sup.2 (Japanese Patent Application Kokai (Laid-Open) Nos. 291443/86 and 286946/89).
The present inventors had found that there can be obtained a hardened material having a bending strength of several hundred kgf/cm.sup.2 or even as high as 1,000 kgf/cm.sup.2 under the favorable conditions, by merely kneading and molding an inorganic substance such as blast furnace slag powder, clay or talc with a water-soluble polymer, water and an optional alkali, and then drying the molded material, and had applied for a patent as to this finding. However such a hardened material had the problems that it was poor in resistance to water and humidity, excessively lowered in strength under high humidity and caused to dissolve from its surface when immersed in water, probably because such a material has not undergone hydration.
The present inventors have made strenuous studies for obtaining a high-strength water-resistant hardened material mainly composed of blast furnace slag powder and have consequently achieved the present invention.